Yes, increasing resolution does have anti-aliasing effect, but increasing resolution from 3x to 4x will not have same effect as increasing AA from 4x SSAA to 9x SSAA - former will have less of anti-aliasing effect.

I think AA is broken in Dolphin. I noticed no difference in quality with it on or off. Even on my rig its a major FPS killer. Setting it to 2x does nothing but going from 2x-4x AA lowers my fps down by 15. Not to mention it doesn't do anything to boot. I wonder why its in the emulator to begin with. I notice with 16x AA to none makes no difference. The only thing it does is give you insanely low unplayable FPS speeds. Its useless IMO.